Interventional techniques have been developed wherein catheters are used to perform diagnostic and therapeutic procedures, such as stenting and angioplasty. During such procedures, thrombus, plaque, or other material may be released into the bloodstream as emboli. If free to circulate through the body, emboli may become lodged in the smaller distal vessels often with serious consequences, thereby presenting a risk of life-threatening or limb threatening ischemia.
U.S. Pat. No. 5,011,488 to Ginsburg, for example, describes a catheter designed to remove frangible thrombus from a vessel, such as from a A-V fistula, to restore flow through the vessel and reduce the risk that thrombus may dislodge and migrate to other regions of the patient's vasculature. The catheter comprises three concentrically arranged flexible tubes, wherein the innermost tube has at its distal end an expandable body and the central tube has an expandable funnel-shaped member. In operation, the funnel-shaped member is deployed proximal of the thrombus while the innermost tube and expandable member are advanced to a position distal of the thrombus. The expandable member then is deployed to contact the vessel wall and retracted proximally to urge the thrombus into the funnel-shaped member. U.S. Pat. No. 5,102,415 to Guenther et al. describes another multi-catheter device for use in removing blood clots.
The devices described in the foregoing patents have several disadvantages that limit their utility. First, the presence of multiple concentric catheters increases the delivery profile and rigidity of the device. Second, the devices are configured primarily to remove frangible thrombus, and are expected to be unsuitable for removing calcified or dense lesions without inflicting trauma to the vessel endothelium. Third, the configuration of the funnel-shaped components and retractable innermost catheter are incompatible with dilatation or stent delivery functionality.
U.S. Pat. No. 5,549,626 to Miller et al. describes a vena cava filter including a self-expanding mesh basket affixed to the distal end of an inner catheter enclosed within a delivery sheath. Suction may be applied through the inner catheter to remove emboli captured in the basket. As in the Ginsburg and Guenther patents, the device described in Miller is not appropriate for use in connection with stent delivery or vessel dilatation.
U.S. Pat. No. 4,723,549 to Wholey describes a catheter having an expandable filter mounted to the catheter shaft distal to a dilatation balloon. The filter comprises a plurality of ribs that are preformed to stow against the catheter. A balloon located between the ribs and catheter causes the ribs to deploy radially outward when inflated. The ribs and filter return to the collapsed position when the balloon is deflated.
The device described in the foregoing Wholey patent contemplates antegrade blood flow, i.e., in a proximal to distal direction along the catheter shaft. Accordingly, the device described in the Wholey patent would not be suitable for capturing emboli in the retrograde access applications, such as in the iliac arteries. In addition, there is a risk that, when the balloon deflates and the ribs collapse against the catheter shaft, some of the emboli collected in the filter may be squeezed past the end of the filter and escape into the bloodstream.
U.S. Pat. No. 6,042,598 to Tsugita et al. describes a variety of percutaneous catheter-based embolic filters. That patent discloses a number of filters that may be deployed from a distal end of a catheter. Like the filter in the aforementioned Wholey patent, however, such filters are not suitable for retrograde access applications, because the emboli are generally released downstream of the filters. In addition, FIG. 10 of Tsugita et al. depicts a catheter for use in retrograde access applications in which the filter assembly is coupled directly to the outer surface of the catheter. Such an arrangement is undesirable because it permits movements of the catheter to be directly transferred to the filter, thus creating the risk that emboli may escape past the outer edge of the filter. More importantly, however, the filter described with respect to FIG. 10 does not provide any mechanism for preventing large amounts of embolic material from being squeezed out of the filter by the sheath during filter contraction and removal of the catheter.
U.S. Patent Application Publication No. US2002/0095172 to Mazzocchi et al. describes various embolic filters that attempt to prevent emboli from escaping filters when they are contracted for removal. The filter of FIGS. 13-15 comprises a basket having a cover slidably disposed to engage the basket and thereby retain emboli within the filter. However, the relative complexity of the filters described in that application would appear to limit the utility of those designs.
In view of the foregoing, it would be desirable to provide a catheter for use in an interventional procedure in retrograde access applications, such as the iliac vessels, wherein the catheter has an embolic protection capability and provides a reduced insertion profile.
In view of the foregoing, it would be desirable to provide a catheter for use in an interventional procedure in retrograde access applications, such as the iliac vessels, wherein the catheter has an embolic protection capability and a simple design that avoids the use of multiple concentric catheters.
It further would be desirable to provide a catheter for use in an interventional procedure in retrograde access applications, wherein the catheter has an embolic protection capability and does not require suction or aspiration, thereby obviating the need to provide a suction or aspiration lumen and enabling a smaller insertion profile.
It also would be desirable to provide a catheter for use in an interventional procedure in retrograde access applications, wherein the catheter has an embolic protection capability and reduces the risk that emboli will be dislodged from the device during filter contraction and removal of the catheter.